Mark Leal wanted to dress up the 348 engine in his '59 Impala but couldn't find any contemporary-style aftermarket valve covers for 348/409 applications. So, decided he'd "whittle away" on some aluminum to see what he could build on his own.

He's been to a lot of Ron Covell metalworking workshops and felt confident enough to tackle the job. Not having a shop full of metal-forming tools, or Covell's talent at freehanding sheetmetal, Mark came up with a simple forming jig, to make the job a little simpler. The only tools required were a bandsaw, a router, and a TIG welder, along with simple handtools. The only special skill is being able to weld aluminum with an acetylene torch. Mark photographed the process, step by step, to share his idea with other 348/409 Chevy owners. Follow along.

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Aluminum WeldingWhile the valve covers seen here were TIG-welded, it's possible to MIG-weld aluminum with the right equipment. It may be possible to convert your MIG welder with different shielding gas (100 percent argon is required for aluminum) and accessories, though purchasing a spool gun from Miller is by far the easiest way we've seen of late. However, this will obviously depend on you owning or considering purchasing a Miller welder! We'll show these two options further on, but let's take a look at the differences between aluminum and steel, and why the former is considerably harder to weld, whether by MIG or TIG.

Unlike steel, aluminum will not tolerate paint, oxidation, grease, or other contaminants when being welded. Correct surface preparation is vital to remove lubricants or dirt, and can be tackled using solvents. Removing any oxides is of equal importance after degreasing. When exposed to air, aluminum forms a hard oxide layer on its surface. The melting point of this layer is roughly three times that of aluminum-3,700 degrees Fahrenheit compared to 1,200 degrees-and this is why the oxide layer must be removed prior to welding, using a stainless steel wire brush. It's important to use a brush that will only ever be used to clean aluminum, to keep from contaminating the weld site.

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You should also be aware of the specific alloy you wish to weld, as the quality of the finished weld will be enhanced by using a filler wire recommended for that particular alloy. ER4043 and ER5356 are the most readily available from local welding supply houses, and they come in various size spools, just as regular filler wire does for welding steel. ER4043 contains silicone, while ER5356 has magnesium content. This allows the latter to have a faster melt-off rate. It is stiffer and easier to feed and is preferable in rigid, high-strength applications. ER4043 is popular, as it is adaptable to many aluminum base metals and is ideal for non-critical work. As with steel filler wire, different wire diameters are available, and owing to aluminum filler wire's soft nature, a thicker wire will feed more easily. The thickness of the material to be welded is a consideration, too, as it's difficult to weld aluminum thinner than 14-gauge without specialized equipment.

Miller Electric Mfg.Miller has introduced the Spoolmate 100 Series spool gun to be used in conjunction with its MIG welders in order to weld aluminum. Full details on how to use the spool gun can be found on Miller's Web site, but suffice it to say, there are some differences compared to a normal MIG welder when used to weld steel. It requires a 10- to 15-degree push travel angle to place the shielding gas in front of the bead, with the contact tip recessed 1/8-inch inside the nozzle. While you may be used to welding steel with 1/8- to 1/4-inch of wire sticking out from the contact tip, aluminum requires 3/8- to 1/21/2-inch. Large beads should be avoided on aluminum, and torch travel speed should be greater than when welding steel, since the material becomes heated, though heat needs to build up at first before travel speed is picked up.